The use of batteries or accumulators is a factor which limit the features of the apparatus, for all applications, and in particular for a watch. Indeed, changing or recharging the batteries or accumulators affects the availability and reliability of the watch.
In this context, the conventional mechanical watch has a certain advantage in watchmaking know-how: such a watch is permanently available. The recharge of powerxe2x80x94which is purely mechanicalxe2x80x94is achieved simply by rewinding the watch mechanism.
This type of watch uses a manual or automatic winding device generally coupled to a regulating device commonly called a xe2x80x9cSwiss lever escapementxe2x80x9d. It is difficult to obtain a high level of precision with this regulating device. This system is also relatively expensive.
The other large family concerns the conventional quartz watch. A battery simultaneously powers an electric motor and a device for regulating the working of the motor. The motor rotation is driven/controlled by a nominal frequency supplied by a quartz. This provides a high level of precision for the time indication. However, this device is relatively noisy since the forward movement of the second wheel is intermittent and the battery has to be changed periodically.
New types of watch have been made combining the two aforecited systems and exploiting their respective advantages. In these constructions, mechanical power storage has been associated with quartz regulation, supplied with electric power by a generator driven by a mechanical part coupled with a power storage spring.
The article by M M Born, Dinger and Farine xe2x80x9cSaltoxe2x80x94An automatically wound mechanical movement with the precision of a quartz movementxe2x80x9d which appeared in the Swiss Chronometry Society publication xe2x80x9cSSC study days 1997xe2x80x9d, pages 55 to 63 may also be cited as the corresponding state of the art.
The arrangement of the generator according to this prior art is illustrated in FIG. 1 annexed hereto, showing a top view of a partially assembled clockwork movement, and in FIG. 2 annexed hereto, which is a transverse cross-section of FIG. 1. This generator includes a rotor with two flanges 8 arranged on either side of three flat coils 11 forming the stator and offset by 120xc2x0 with respect to each other relative to the rotor axis, in the same orthogonal plane as the latter.
Six magnets 9 are fixed radially and at regular intervals on each flange 8, facing coils 11. Two consecutive or facing magnets 9 have opposite polarity. A printed circuit 6 is secured to plate 4 and is used as a support for coils 11.
Electric circuit 10, which has a low power consumption, is powered by an electric generatorxe2x80x94formed by the shaft assembly of rotor 5, flanges 8, magnets 9 and coils 11xe2x80x94driven via the kinematic connection 3 by barrel device 2. The mechanical power stored in barrel 2 thus drives the rotor. The passage of magnets 9 in proximity to coils 11 generates a substantially sinusoidal induced voltage at the terminals of coils 11.
The voltage supplied by a coil 11 is substantially sinusoidal. The operation of the regulation device requires a rectified voltage. The voltage across the terminals of coils 11 used to supply the electronic regulation circuit 10 passes through an electrical rectifier circuit. The voltage then passes through an amplifier step which for example quadruples the output voltage of the rectifier.
Since clockwork movements are generally of small size, inevitable manufacturing and mounting imprecision affects the stability of the output voltage of the rectifier circuit. The amplifier step amplifies the voltage variations in the same order of magnitude. In order to obtain a rectified voltage sufficient for all the movements with a generator of one series, a significant margin of error is therefore kept by increasing the minimum value provided for the rectified voltage.
The higher the margin of error on the rectified voltage, the higher the minimum voltage has to be for normal operation, which results in a higher electrical power consumption in the regulation circuit and a decrease in the autonomy of the watch between two winding operations of the barrel mechanism 2.
The object of the invention is to overcome this drawback. The invention therefore concerns a clockwork movement fitted with a generator formed of a rotor including two flanges connected by a shaft, magnets being fixed to each flange in even numbersxe2x80x94two consecutive or facing magnets having opposite polarity. This generator further includes a stator including one or a plurality of coils with axes parallel to that of the rotor, this coil or this plurality of coils being introduced between the two flanges fitted with magnets and being supported by a substrate. This movement is characterized in that at least one part of the stator including said coil or at least one coil of said plurality is fitted with means allowing it to be moved so as to make its position adjustable relative to the rotor in a plane perpendicular to the shaft of said rotor, so as to adjust the amplitude of the induced voltage across the terminals of said coil or at least one coil of said plurality when the rotor rotates.
The support substrate of the coil(s) can be made either in a single piece or in several and can include oblong drillings which are longitudinal or in an arc of circle and which act as guides for the adjustment.
An eccentric stop device advantageously allows the adjustment of the voltage across the coil or coils to be adjusted and the disposition of the coils to be memorised in the event the generator is dismantled.
The invention will be understood and other advantages will appear from the following description of non limitating embodiment examples made with reference to the annexed schematic drawings in which: